In a communication system, a channel quality indicator (Channel Quality Indicator, CQI in short) generally describes channel quality during transmission on a specific bandwidth, it can be used for link adaptation and scheduling, and it is crucial for acquiring a channel property and thus improving throughput of the system. In addition, for a system with precoding, the CQI is also calculated based on a precoding matrix, where the precoding matrix is generally indicated by one or more indexes, such as a precoding matrix indicator (Precoding Matrix Indicator, PMI in short) and layer number of a precoding matrix or a rank indication (Rank Indication, RI in short). In the 3rd Generation Partnership Project (The 3rd Generation Partnership Project, 3GPP in short) long term evolution (Long Term Evolution, LTE) system, a user equipment (User Equipment, UE in short) feeds channel state information (Channel State Information, CSI in short) back to an evolved node B (Evolved Node B, eNB in short), where the CSI includes CQI/PMI/RI. In addition, the eNB below may include a macro base station and a low power node, such as a micro base station (Micro), a pico base station (Pico), a remote radio head (Remote Radio Head, RRH), a relay device (Relay) and a femto base station (Femto) and an access point (Access Point).
The existing LTE system feeds back CSI information in different frequency domain granularities. The whole system bandwidth is divided into multiple subbands, where each subband consists of one or more resource blocks (Resource Block, RB in short), CQI/PMI of each subband is calculated and called a subband CQI/PMI; or CQI/PMI of the whole system bandwidth is calculated and called a wideband CQI/PMI. The RI is generally calculated for the whole system bandwidth.
However, in the existing manner of feeding back a subband CQI, subbands indicated by the subband CQIs do not overlap with each other, that is to say, RBs forming one subband are different from RBs forming another subband. The subband CQI is generally acquired by utilizing a signal to interference plus noise ratio (Signal to Interference plus Noise Ratio, SINR in short) on each RB included in the subband, due to channel correlation, the subband CQI will better reflect channel quality of each RB in the center of the subband, and may deviate from channel quality corresponding to an RB on the edge of the subband.
Therefore, in the prior art, the eNB cannot perform frequency-selective scheduling or link adaptation well to an RB on the edge of the subband. Besides, multiple-user pairing in a multiple user-multiple input multiple output (Multiple User-Multiple Input Multiple Output, MU-MIMO) transmission can be further influenced, and thereby reducing system throughput.